HVAC system operated with adaptive discharge air temperature setpoint

ABSTRACT

An HVAC system includes a blower, a variable-speed compressor, an indoor air temperature sensor that measures an indoor air temperature (IAT) of an enclosed space, a discharge air temperature sensor that measures a discharge air temperature (DAT) of the flow of air from an evaporator, and a controller. The controller stores an indoor temperature setpoint and a default discharge air temperature setpoint. The controller receives the IAT and the DAT. The controller determines that the IAT is not within a threshold range of the indoor temperature setpoint. The controller then determines an adaptive discharge air temperature setpoint. The controller determines a compressor speed at which to operate the variable-speed compressor based on the adaptive discharge air temperature setpoint. The controller causes the variable-speed compressor to operate at the determined compressor speed.

TECHNICAL FIELD

The present disclosure relates generally to heating, ventilation, andair conditioning (HVAC) systems and methods of their use. In certainembodiments, the present disclosure relates to an HVAC system operatedwith adaptive discharge air temperature setpoint.

BACKGROUND

Heating, ventilation, and air conditioning (HVAC) systems are used toregulate environmental conditions within an enclosed space. In a coolingmode operation of the HVAC system, a flow of air may be cooled via heattransfer with refrigerant and returned to the enclosed space as cooledconditioned air.

SUMMARY OF THE DISCLOSURE

Previous HVAC systems may fail to reach target or setpoint airtemperatures, even when the system has unused cooling capacity (e.g.,when additional compressor capacity is available). Previous HVAC systemsmay also or alternatively be slow to provide cooling when there is asudden change in load, such as when the system switches from an idlestate to a cooling state or when the setpoint temperature is decreased.HVAC systems which operate a blower in a control loop based on indoortemperature and compressor(s) in a separate control loop based ondischarge air temperature may be particularly prone to the problemsdescribed above. Indoor air temperature refers to a temperature of airin an enclosed space into which conditioned air is provided, anddischarge air temperature refers to a temperature of air downstream ofan evaporator of the HVAC system. Using previous technology, a targetindoor temperature may be reached only very slowly or may never bereached.

This disclosure solves problems of previous technology, including thosedescribed above, using an adaptive discharge air temperature setpoint.When a controller of the HVAC system determines that an indoortemperature setpoint is not being reached, an adaptive discharge airtemperature is determined. Compressor(s) of the HVAC system are thenoperated based on this adaptive setpoint to provide improved cooling.The adaptive discharge air temperature setpoint may be used at leastuntil the indoor setpoint temperature is reached. The systems andmethods described in this disclosure may be integrated into a practicalapplication of an adaptive HVAC controller that provides faster and morereliable indoor air temperature control for HVAC systems operatingseparate control mechanisms for a blower based on indoor air temperatureand compressor(s) based on discharge air temperature. The HVAC system ofthis disclosure may operate at an increased cooling capacity when neededin order to reach comfortable indoor temperature more rapidly. The useof an adaptive discharge air temperature setpoint by the HVAC systemcontroller ensures that an indoor setpoint is reached under conditionsin which previous systems may fail to provide adequate cooling to thespace. Certain embodiments may include none, some, or all of the abovetechnical advantages. One or more other technical advantages may bereadily apparent to one skilled in the art from the figures,descriptions, and claims included herein.

In an embodiment, a heating, ventilation and air conditioning (HVAC)system includes a blower configured to provide a flow of air across anevaporator of the HVAC system, a variable-speed compressor configured tocompress a refrigerant flowing through the HVAC system, an indoor airtemperature sensor positioned and configured to measure an indoor airtemperature (IAT) of the enclosed space, a discharge air temperaturesensor positioned and configured to measure a discharge air temperature(DAT) of the flow of air downstream of the evaporator, and a controller.A memory of the controller stores an indoor temperature setpoint and adefault discharge air temperature setpoint. The controller receives theIAT and the DAT. The controller determines, based on a differencebetween the received IAT and the indoor temperature setpoint, that theIAT is not within a threshold range of the indoor temperature setpoint.After determining that the IAT is not within the threshold range of theindoor temperature setpoint, the controller determines an adaptivedischarge air temperature setpoint based on the default discharge airtemperature setpoint and the difference between the received IAT and theindoor temperature setpoint. The controller determines a compressorspeed at which to operate the variable-speed compressor based on theadaptive discharge air temperature setpoint. The controller causes thevariable-speed compressor to operate at the determined compressor speed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram of an example HVAC system configured for controlusing an adaptive discharge air temperature setpoint;

FIG. 2 is a flow diagram illustrating the determination of an adaptivedischarge air temperature setpoint using the HVAC system illustrated inFIG. 1;

FIG. 3 is a plot illustrating an example adaptive discharge airtemperature setpoint as a function of the difference or offset betweenindoor air temperature and the indoor temperature setpoint;

FIG. 4A is a plot illustrating example performance of an HVAC systemoperated without an adaptive discharge air temperature setpoint;

FIG. 4B is a plot illustrating example performance of the same HVACsystem of FIG. 4A operated with an adaptive discharge air temperaturesetpoint;

FIG. 5 is a flowchart illustrating an example method of operating theexample HVAC system illustrated in FIG. 1 using an adaptive dischargeair temperature setpoint; and

FIG. 6 is a diagram of the controller of the example HVAC systemillustrated in FIG. 1.

DETAILED DESCRIPTION

Embodiments of the present disclosure and its advantages are bestunderstood by referring to FIGS. 1 through 6 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

As described above, prior to the present disclosure, a target indoortemperature may be reached only very slowly or may never be reachedusing previous technology. The HVAC system illustrated in FIG. 1 anddescribed below overcomes this technical problem of previous technologyby operating using an adaptive discharge air temperature setpoint. FIGS.2 and 3 illustrate the determination of an adaptive discharge airtemperature setpoint for operating of the HVAC system of FIG. 1. FIGS.4A and 4B illustrate the improved performance of an example HVAC systemconfigured according to the example of FIG. 1. The example HVAC systemreaches a target indoor setpoint temperature more rapidly when operatedusing the adaptive discharge air temperature setpoint (FIG. 4B) than waspossible using previous technology without an adaptive DAT setpoint (asin FIG. 4A). FIG. 5 illustrates an example method of operating thesystem of FIG. 1. FIG. 6 illustrates an example controller for the HVACsystem of FIG. 1.

HVAC System

FIG. 1 is a schematic diagram of an embodiment of an HVAC system 100with a controller 142 configured to determine an adaptive discharge airtemperature (DAT) setpoint 156 and operate the HVAC system 100 using theadaptive DAT setpoint 156. For example, the HVAC system 100 may use theadaptive DAT setpoint 156 to determine compressor instructions 160 formore effectively operating one or more compressors 106 a,b of the HVACsystem 100. Operation using the adaptive DAT setpoint 156 facilitatesreaching an indoor air temperature (IAT) setpoint 138 more rapidly andmore reliably than was possible using previous technology. The HVACsystem 100 generally conditions air for delivery to a conditioned space.The conditioned space may be, for example, a room, a house, an officebuilding, a warehouse, or the like. In some embodiments, the HVAC system100 is a rooftop unit (RTU) that is positioned on the roof of a buildingand the conditioned air is delivered to the interior of the building. Inother embodiments, portion(s) of the system 100 may be located withinthe building and portion(s) outside the building. The HVAC system 100may include one or more heating elements, not shown for convenience andclarity. The HVAC system 100 may be configured as shown in FIG. 1 or inany other suitable configuration. For example, the HVAC system 100 mayinclude additional components or may omit one or more components shownin FIG. 1.

The HVAC system 100 includes a working-fluid conduit subsystem 102, atleast one condensing unit 104, an expansion device 114, an evaporator116, a blower 128, a thermostat 136, and a controller 142. Theworking-fluid conduit subsystem 102 facilitates the movement of aworking fluid (e.g., a refrigerant) through a cooling cycle such thatthe working fluid flows as illustrated by the dashed arrows in FIG. 1.The working fluid may be any acceptable working fluid including, but notlimited to hydroflurocarbons (e.g., R-410A) or any other suitable typeof refrigerant.

The condensing unit 104 includes one or more compressors 106 a,b, acondenser 108, and a fan 110. In some embodiments, the condensing unit104 is an outdoor unit while at least a portion of the other componentsof system 100 may be located indoors. The compressor(s) 106 a,b is/arecoupled to the working-fluid conduit subsystem 102 and compresses (i.e.,increases the pressure of) the working fluid. The compressor(s) 106 a,bof condensing unit 104 may be a single-stage compressor, avariable-speed compressor, or a multi-stage compressor. In someembodiments, the HVAC system 100 includes a first compressor 106 a thatis a variable-speed compressor. A variable-speed compressor is generallyconfigured to operate at different speeds (e.g., based on compressorinstructions 160 described below) to increase the pressure of theworking fluid to keep the working fluid moving along the working-fluidconduit subsystem 102. The speed of the variable-speed compressor 106 acan be modified (e.g., based on compressor instructions 160) to adjustthe cooling capacity of the HVAC system 100. In some embodiments, theHVAC system 100 also includes a second compressor 106 b that is anyappropriate type of compressor (e.g., single-stage or variable-speed).For example, if the variable-speed compressor 106 a cannot reach atarget speed indicated by the compressor instructions 160, thecontroller 142 may cause the second compressor 106 b to activate toprovide further compression of the working fluid. In embodiments withtwo or more compressors 106 a,b the compressors 106 a,b may be in seriesor in parallel (e.g., in one or more additional condensing units 104,not shown for clarity and conciseness).

The compressor(s) 106 a,b is/are in signal communication with thecontroller 142 using wired and/or wireless connection. The controller142 provides compressor instructions 160, which include commands and/orsignals to control operation of the compressor(s) 106 a,b. Thecontroller 142 may receive signals from the compressor(s) 106 a,b, forexample, corresponding to a status of the compressor(s) 106 a,b. Forexample, when the compressor 106 a is a variable-speed compressor, thecontroller 142 may provide compressor instructions 160 indicating acompressor speed (e.g., compressor speed 610 of FIG. 6) at which tooperate the compressor 106 a. If the compressors 106 a,b operate as amulti-stage compressor, the compressor instructions 160 may include anindication of which compressors 106 a,b to turn on and off, based on theadaptive DAT setpoint 156 (described further below). The controller 142may operate the compressor(s) 106 a,b in different modes correspondingto load conditions (e.g., the amount of cooling or heating requestedfrom the HVAC system 100), whether a cooling or dehumidification mode ofoperation is requested, and the like. The controller 142 and itscomponents are described in greater detail below and with respect toFIG. 6.

The condenser 108 is configured to facilitate movement of the workingfluid through the working-fluid conduit subsystem 102. The condenser 108is generally located downstream of the compressor(s) 106 a,b and isconfigured to remove heat from the working fluid. The fan 110 isconfigured to move air 112 across the condenser 108. For example, thefan 110 may be configured to blow outside air through the condenser 108to help cool the working fluid flowing therethrough. The fan 110 may bein communication with the controller 142 (e.g., via wired and/orwireless communication) to receive control signals for turning the fan110 on and off and/or adjusting a speed of the fan 110. For example, thecompressor instructions 160 may also include an indication of a speed atwhich the fan 110 should rotate. The compressed, cooled working fluidflows from the condenser 108 toward the expansion device 114.

The expansion device 114 is coupled to the working-fluid conduitsubsystem 102 downstream of the condenser 108 and is configured toremove pressure from the working fluid. In this way, the working fluidis delivered to the evaporator 116 and receives heat from airflow 118 toproduce a conditioned airflow 120 that is delivered by a duct subsystem122 to the conditioned space. In general, the expansion device 114 maybe a valve such as an expansion valve or a flow control valve (e.g., athermostatic expansion valve (TXV)) or any other suitable valve forremoving pressure from the working fluid while, optionally, providingcontrol of the rate of flow of the working fluid. The expansion device114 may be in communication with the controller 142 (e.g., via wiredand/or wireless communication) to receive control signals for openingand/or closing associated valves and/or to provide flow measurementsignals corresponding to the rate of working fluid flow through theworking-fluid conduit subsystem 102.

The evaporator 116 is generally any heat exchanger configured to allowor facilitate heat transfer between air flowing through (or across) theevaporator 116 (i.e., air of airflow 118 contacting an outer surface ofone or more coils of the evaporator 116) and working fluid passingthrough the interior of the evaporator 116. The evaporator 116 mayinclude one or more circuits of coils. The evaporator 116 is fluidicallyconnected to the compressor(s) 106 a,b, such that working fluidgenerally flows from the evaporator 116 to the condensing unit 104.

A portion of the HVAC system 100 is configured to move airflow 118provided by the blower 128 across the evaporator 116 and out of the ductsub-system 122 as conditioned airflow 120. Return air 124, which may beair returning from the building, fresh air from outside, or somecombination, is pulled into a return duct 126. A suction side of theblower 128 pulls the return air 124. The blower 128 discharges airflow118 into a duct 130 such that airflow 118 crosses the evaporator 116 orheating elements (not shown) to produce conditioned airflow 120. Theblower 128 is any mechanism for providing airflow 118 through the HVACsystem 100. For example, the blower 128 may be a variable-speedcirculation blower or fan. Examples of a variable-speed blower include,but are not limited to, belt-drive blowers controlled by inverters,direct-drive blowers with electronic commuted motors (ECM), or any othersuitable type of blower. The blower 128 is in signal communication withthe controller 142 using wired and/or wireless connection. Thecontroller 142 provides a blower speed 148 (described further below) atwhich to operate the blower 128 (e.g., a rate of rotation at which tooperate the blower 128, an amount of power to supply to a motor of theblower 128, or the like).

The HVAC system 100 includes one or more sensors 132, 134 in signalcommunication with controller 142 (e.g., via wired and/or wirelessconnection). Sensors 132, 134 may include any suitable type of sensorsfor measuring air temperature, relative humidity, and/or any otherproperties of a conditioned space (e.g. a room or building). In theexample of FIG. 1, sensor 132 is positioned and configured to measure adischarge air temperature (DAT) 154 of the airflow 120 provided from theevaporator 116 or to the conditioned space (e.g., in or near duct 122).Sensor 134 is positioned and configured to measure an indoor airtemperature (IAT) 144 of air in the conditioned space. In someembodiments, the sensor 134 may embedded within or in communication withthe thermostat 136. One or more additional sensors (not shown forclarity and conciseness) may be positioned anywhere within theconditioned space, the HVAC system 100, and/or the surroundingenvironment. As an example, the HVAC system 100 may include sensorspositioned and configured to measure any other suitable type of airtemperature (e.g., the temperature of air at one or more locationswithin the conditioned space and/or an outdoor air temperature) or otherproperty (e.g., a relative humidity of air at one or more locationswithin the conditioned space or outdoors).

The HVAC system 100 includes one or more thermostats 136, for example,located within the conditioned space (e.g. a room or building). Athermostat 136 is generally in signal communication with the controller142 using any suitable type of wired and/or wireless connection. Also oralternatively, one or more functions of the controller 142 may beperformed by the thermostat 136. For example, the thermostat 136 mayinclude the controller 142. The thermostat 136 may be a single-stagethermostat, a multi-stage thermostat, or any suitable type ofthermostat. The thermostat 136 is configured to allow a user to input adesired temperature or indoor air temperature (IAT) setpoint 138 for theconditioned space and/or for a designated space or zone such as a roomin the conditioned space. The controller 142 may use information fromthe thermostat 136 such as the temperature setpoint 138 for controllingthe compressor(s) 106 a,b and the blower 128, as described in greaterdetail below.

In some embodiments, the thermostat 136 may include a user interface anddisplay for displaying information related to the operation and/orstatus of the HVAC system 100. For example, the user interface maydisplay operational, diagnostic, and/or status messages and provide avisual interface that allows at least one of an installer, a user, asupport entity, and a service provider to perform actions with respectto the HVAC system 100. For example, the user interface may provide forselection and/or display of an operating mode 140 of the HVAC system100. The mode 140 may correspond to whether the HVAC system 100 isoperating to provide cooling (in a cooling mode 140), is operating toprovide dehumidification (in a dehumidification mode 140), is operatingto provide heating (in a heating mode 140), is operating with anadaptive DAT setpoint 156 (e.g., in an adaptive discharge setpoint mode140), or the like. The user interface may display other information suchas the indoor air temperature 144, indoor air temperature setpoint 138,one or more alerts, and/or other messages related to the status and/oroperation of the HVAC system 100 and/or its components.

As described in greater detail below with respect to FIGS. 2-6, thecontroller 142 is configured to store the indoor air temperaturesetpoint 138 (e.g., received from the thermostat 136) and a defaultdischarge air temperature setpoint (e.g., one or both of setpoints 202,204 of FIG. 2). The controller 142 may be implemented using theprocessor, memory, and input/output interface described with respect toFIG. 6 below. The controller 142 receives measurements of the indoor airtemperature 144 (e.g., from sensor 134) and discharge air temperature154 (e.g., from sensor 132). The controller 142 determines, using indoortemperature comparator 146, a difference or offset 150 between theindoor air temperature 144 and the indoor air temperature setpoint 138.The comparator 146 is configured to compare (e.g., by determining adifference, ratio, or any other appropriate value) the indoor airtemperature 144 and the indoor air temperature setpoint 138. Thecontroller 142 may determine a blower speed 148 at which to operate theblower 128 based on the measured indoor air temperature 144 and theindoor air temperature setpoint 138 (e.g., based on offset 150). Thedetermined blower speed 148 may be provided to the blower 128 in orderto cause the blower 128 to operate at the determined blower speed 148,as illustrated in FIG. 1.

If the offset 150 is not within a predefined temperature range (e.g., athreshold temperature range included in the thresholds 608 of FIG. 6),an adaptive DAT setpoint 156 is determined using the adaptive setpointgenerator 152. In some embodiments, the adaptive DAT setpoint 156 isdetermined when the measured indoor air temperature 144 is greater thanthe indoor air temperature setpoint 138 (i.e., such that operation in acooling mode 140 is appropriate) and the offset 150 is not within thepredefined temperature range.

The adaptive DAT setpoint 156 is determined based on one or more defaultDAT setpoints (e.g., setpoints 202, 204 of FIG. 2) and the offset 150,as described with respect to the examples of FIGS. 2 and 3 below. Themeasured DAT 154 is compared to the adaptive DAT setpoint 156, using DATcomparator 158, to determine compressor instructions 160. The comparator158 is configured to compare (e.g., by determining a difference, ratio,or any other appropriate value) the DAT 154 and the adaptive DATsetpoint 156. For instance, if the measured DAT 154 is a first thresholdamount above the adaptive DAT setpoint 156, the compressor instructions160 may cause the variable-speed compressor 106 a to operate at a firstspeed to increase cooling provided by the HVAC system 100. If themeasured DAT 154 is a second threshold amount (where the secondthreshold amount is larger than the first threshold amount) above theadaptive DAT setpoint 156, the compressor instructions 160 may cause thevariable-speed compressor 106 a to operate at a second speed that isfaster than the first speed to further increase cooling provided by theHVAC system 100. In some embodiments, following causing thevariable-speed compressor 106 a to operate according to the compressorinstructions 160, the indoor air temperature 144 reaches a value that iswithin a threshold value (e.g., a threshold 608 of FIG. 6) of the indoorair temperature setpoint 138 within a threshold time (see exampleresults of FIGS. 4A and 4B). For example, the indoor air temperature 144may be within 0.5° F. of the indoor air temperature setpoint 138 withinabout 15 minutes. As such, the indoor air temperature setpoint 138 maybe reached more quickly using the HVAC system 100 with the adaptive DATsetpoint 156 than was possible using previous technology.

In some embodiments, the controller 142 may cause a second compressor106 b to activate (e.g., if the variable-speed compressor cannotcomplete the determined compressor instructions 160). For instancereferring to the examples above, if the measured DAT 154 is a thirdthreshold amount (where the third threshold amount is larger than thesecond threshold amount) above the adaptive DAT setpoint 156, thecompressor instructions 160 may cause the second compressor 106 b toactivate to provide further cooling capacity to the HVAC system 100. Asanother example, if the controller 142 determines that a compressorspeed indicated by the compressor instructions 160 (e.g., compressorspeed 610 of FIG. 6) is greater than a maximum speed (e.g., the maximumspeed 612 of FIG. 6) of the variable-speed compressor 106 a, then thecontroller 142 may cause the variable-speed compressor 106 a to operateat its maximum speed and the second compressor 106 b to activate. Thesecond compressor 106 b provides supplemental cooling capacity to theHVAC system 100.

In certain embodiments, connections between various components of theHVAC system 100 are wired. For example, conventional cable and contactsmay be used to couple the controller 142 to the various components ofthe HVAC system 100, including, the compressor 106, the expansion device114, the blower 128, sensors 132, 134, and thermostat(s) 136. In someembodiments, a wireless connection is employed to provide at least someof the connections between components of the HVAC system 100. In someembodiments, a data bus couples various components of the HVAC system100 together such that data is communicated there between. In a typicalembodiment, the data bus may include, for example, any combination ofhardware, software embedded in a computer readable medium, or encodedlogic incorporated in hardware or otherwise stored (e.g., firmware) tocouple components of HVAC system 100 to each other. As an example andnot by way of limitation, the data bus may include an AcceleratedGraphics Port (AGP) or other graphics bus, a Controller Area Network(CAN) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect,an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, aMicro Channel Architecture (MCA) bus, a Peripheral ComponentInterconnect (PCI) bus, a PCI-Express (PCI-X) bus, a serial advancedtechnology attachment (SATA) bus, a Video Electronics StandardsAssociation local (VLB) bus, or any other suitable bus or a combinationof two or more of these. In various embodiments, the data bus mayinclude any number, type, or configuration of data buses, whereappropriate. In certain embodiments, one or more data buses (which mayeach include an address bus and a data bus) may couple the controller142 to other components of the HVAC system 100.

In an example operation of the HVAC system 100, the controller 142determines that the indoor air temperature 144 is greater than theindoor air temperature setpoint 138 and starts up the HVAC system 100 toprovide cooling to the space. The HVAC system 100 may initially operatein a cooling mode 140. The controller 142 instructs the blower 128 tooperate at a blower speed 148. The blower speed 148 may be determinedbased on the indoor air temperature 144 and the indoor air temperaturesetpoint 138. For instance, a control loop (e.g., a PI control loop) maybe implemented to adjust the blower speed 148 to minimize the offset 150between the indoor air temperature 144 and IAT setpoint 138. Meanwhile,the controller 142 also adjusts the compressor instructions 160 tomaintain the discharge air temperature 154 at or near a defaultpredefined value (e.g., the default cooling mode discharge airtemperature setpoint 202 of FIG. 2). For example, a control loop (e.g.,a PI control loop) may be implemented to adjust the compressorinstructions 160 (e.g., the compressor speed 610 of FIG. 6 for thevariable-speed compressor 106 a and optionally instructions to turn onthe second compressor 106 b) to maintain the DAT 154 at or near thedefault predefined value.

During operation of the HVAC system 100, as described above, thecontroller 142 detects that the indoor air temperature 144 is greaterthan the IAT setpoint 138 and that the indoor air temperature offset 150is greater than a threshold value (e.g., a threshold of the thresholds608 of FIG. 6). In response to this determination, the controller 142uses the adaptive setpoint generator 152 to determine an adaptive DATsetpoint 156 with which to determine the compressor instructions 160(e.g., using a control loop as described above). As described withrespect to the examples of FIGS. 4A and 4B, operating the compressor(s)106 a,b using an adaptive DAT setpoint 156 allows the IAT setpoint 138to be reached more rapidly and reliably than was previously possible. Insome cases, operation of the compressor(s) 106 a,b using the adaptiveDAT setpoint 156 may allow the IAT setpoint 138 to be reached when theIAT setpoint 138 could not have been reached using previous technology.

FIG. 2 illustrates an example operation of the adaptive setpointgenerator 152 of FIG. 1 to determine the adaptive DAT setpoint 156. Thecontroller 142 may store (e.g., in memory 604 of FIG. 6) a defaultcooling mode discharge air temperature setpoint 202, a defaultdehumidification mode discharge air temperature setpoint 204, and amaximum temperature differential 206. The default cooling mode dischargeair temperature setpoint 202 is the default predefined value that isused to determine the compressor instructions 160 under normal coolingmode 140 operation (e.g., when an adaptive DAT setpoint 156 is notneeded). The default dehumidification mode discharge air temperaturesetpoint 204 is the default predefined value that is used to determinethe compressor instructions 160 under normal dehumidification mode 140operation (e.g., when an adaptive DAT setpoint 156 is not needed). Themaximum temperature differential 206 is the temperature range of theindoor air temperature offset 150 over which an adaptive DAT setpoint156 is determined.

As illustrated in the example of FIG. 2, the adaptive DAT setpoint 156may be determined using the indoor air temperature offset 150, thedefault discharge air temperature setpoints 202, 204, and/or the maximumtemperature differential 206. FIG. 3 shows an example plot 300 of theadaptive DAT setpoint 156 as a function of the indoor air temperatureoffset 150. The example adaptive DAT setpoint 156 shown in plot 300 hasa value equal to the default cooling mode discharge air temperaturesetpoint 202 until the indoor air temperature offset 150 reaches athreshold value above which the adaptive DAT setpoint 156 is determined.In this example, the threshold value (e.g., the threshold of thresholds608 of FIG. 6) is 0° F. The adaptive DAT setpoint 156 decreases over themaximum temperature differential 206 until it reaches the defaultdehumidification mode discharge air temperature setpoint 204. In theexample of FIG. 3, the adaptive DAT setpoint 156 decreases linearly overthe maximum temperature differential 206. In the example of FIG. 3, thethreshold value for the indoor air temperature offset 150 above which anadaptive DAT setpoint 156 is determined is 0° F. However, this thresholdvalue may be any appropriate value. For instance, if a threshold valueof 1° F. is used, the adaptive DAT setpoint 156 illustrated in FIG. 3would remain at the default cooling mode discharge air temperaturesetpoint 202 value until an indoor air temperature offset 150 of 1° F.is reached. The adaptive DAT setpoint 156 then decreases in value overthe maximum temperature differential 206 until the defaultdehumidification mode discharge air temperature setpoint 204 is reached.Moreover, while the example maximum temperature differential 206 is 1°F. in the example of FIG. 3, the maximum temperature differential 206may be any appropriate value (e.g., from about 0.5° F. to 5° F.).

Returning to the example operation of the HVAC system 100 of FIG. 1, thecontroller 142 uses the adaptive DAT setpoint 156 (e.g., determined asdescribed with respect to FIGS. 2 and 3 above) to determine thecompressor instructions 160. For example, the DAT 154 measured by sensor132 may be compared to the adaptive DAT setpoint 156, using the DATcomparator 158, to determine compressor instructions 160. The differencebetween the measured DAT 154 and the adaptive DAT setpoint 156 may beused to determine the compressor instructions 160, such that thecompressor speed (e.g., compressor speed 610 of FIG. 6) indicated by thecompressor instructions 160 increases when this difference increases. Ifthe controller 142 determines that a compressor speed indicated by thecompressor instructions 160 (e.g., a compressor speed 610 of FIG. 6) isgreater than a maximum speed (e.g., the maximum speed 612 of FIG. 6) ofthe variable-speed compressor 106 a, then the controller 142 may causethe variable-speed compressor 106 a to operate at its maximum speed andcause the second compressor 106 b to activate to provide supplementalcompression.

Example Performance of Systems Configured According to HVAC System 100

As described above with respect to FIGS. 1-3, operating thecompressor(s) 106 a,b using compressor instructions 160 that aredetermined based on the specially selected adaptive DAT setpoint 156 ofthis disclosure allows the indoor air temperature 144 to be reached morerapidly and reliably than was possible using previous technology. Theresults illustrated in FIGS. 4A and 4B demonstrate benefits andimprovements provided by operating an HVAC system using an adaptive DATsetpoint 156. FIG. 4A shows a plot 400 of the indoor air temperature 144as a function of time for an example HVAC system operating using thedefault cooling mode discharge air temperature setpoint 202 withoutusing an adaptive DAT setpoint 156, and FIG. 4B shows a plot 450 of theindoor air temperature 144 as a function of time for the same exampleHVAC system operating using the adaptive DAT setpoint 156. Plots 400,450 also show the indoor air temperature setpoint 138, blower speed 148,and compressor speed 610 indicated by the compressor instructions 160 asa function of time.

In both plots 400, 450, a change in load occurs at time 16.5 hours, suchthat the indoor air temperature 144 increases above the indoor airtemperature setpoint 138. With the system operating based on theadaptive DAT setpoint 156, as shown in plot 450 of FIG. 4B, the indoorair temperature 144 is brought to within less than 0.5° F. of the indoorair temperature setpoint 138 within 15 minutes. In contrast, with thesystem operating without the adaptive DAT setpoint 156, as shown in plot400 of FIG. 4A, the indoor air temperature 144 remaining greater than 1°F. above the indoor air temperature setpoint 138 even after more thanone hour. Plots 400 and 450 demonstrate the improvements achieved byoperating an HVAC system based on adaptive DAT setpoint 156.

Example Method of Operation

FIG. 5 is a flowchart illustrating an example method 500 of operatingthe HVAC system 100 using an adaptive DAT setpoint 156. As describedabove with respect to FIGS. 1-4B, the use of an adaptive DAT setpoint156 may allow the indoor air temperature 144 to be maintained at or nearan indoor air temperature setpoint 138 more rapidly and reliably thanwas possible using previous technology. The method 500 may begin at step502 where the controller 142 of the HVAC system 100 receivesmeasurements of the indoor air temperature 144 from sensor 134 and thedischarge air temperature 154 from sensor 132.

At step 504, the controller 142 determines whether the indoor airtemperature 144 is outside a threshold range (e.g., a threshold range ofthresholds 608 of FIG. 6) of the indoor air temperature setpoint 138.For example, the controller 142 may determine the offset 150 describedwith respect to FIG. 1 and determine whether the offset 150 is greaterthan a threshold value (e.g., a threshold of thresholds 608 of FIG. 6).If the indoor air temperature 144 is not outside the threshold range ofthe indoor air temperature setpoint 138, the controller 142 proceeds tostep 506 and determines the compressor instructions 106 (e.g., includingthe compressor speed 610 of FIG. 6 at which to operate thevariable-speed compressor 106 a of FIG. 1) using the default coolingmode discharge air temperature setpoint 202. In other words, if theindoor air temperature 144 is not outside the threshold range of theindoor air temperature setpoint 138, then an adaptive DAT setpoint 156may not be determined (or the determined adaptive DAT setpoint 154 maybe equal to the default cooling setpoint 202—see FIG. 3). In some cases,the controller 142 may determine the compressor instructions 160 tomaintain the discharge air temperature 154 at or near the defaultcooling mode discharge air temperature setpoint 202. For example, acontrol loop (e.g., a PI control loop) may be implemented to adjust thecompressor instructions 160 (e.g., the compressor speed 610 of FIG. 6for a variable-speed compressor 106 a and optionally instructions toturn on a second compressor 106 b) to maintain the DAT 154 at or nearthe default cooling mode discharge air temperature setpoint 202. Thecompressor instructions 160 are then used to operate the HVAC system 100at steps 512-516.

If, at step 504, the indoor air temperature 144 is outside the thresholdrange of the indoor air temperature setpoint 138, the controller 142proceeds to step 508. At step 508, the controller 142 determines theadaptive DAT setpoint 156. The adaptive DAT setpoint 156 may bedetermined as described above with respect to FIGS. 1-3. For example,the adaptative DAT setpoint 156 may be determined based on the defaultdischarge air temperature setpoints 202, 204 and the difference oroffset 150 between the indoor air temperature 144 and the indoor airtemperature setpoint 138.

At step 510, the controller 142 determines the compressor instructions106 (e.g., the compressor speed 610 of FIG. 6 at which to operate thevariable-speed compressor 106 a of FIG. 1) using the adaptive DATsetpoint 156. For example, a difference between the measured DAT 154 andthe adaptive DAT setpoint 156 from step 508 may be used to determine thecompressor instructions 160. As an example, the determined compressorinstructions 160 may indicate a compressor speed (e.g., compressor speed610 of FIG. 6) that increases when this difference increases. In somecases, the controller 142 may determine the compressor instructions 160to maintain the discharge air temperature 154 at or near the adaptiveDAT setpoint 156 from step 508. For example, a control loop (e.g., a PIcontrol loop) may be implemented to adjust the compressor instructions160 (e.g., the compressor speed 610 of FIG. 6 for a variable-speedcompressor 106 a and optionally instructions to turn on a secondcompressor 106 b) to maintain the DAT 154 at or near the adaptive DATsetpoint 156. If the controller 142 determines that a compressor speedindicated by the compressor instructions 160 (e.g., a compressor speed610 of FIG. 6) is greater than a maximum speed (e.g., the maximum speed612 of FIG. 6) of the variable-speed compressor 106 a, then thecontroller 142 may determine compressor instructions 160 that cause thevariable-speed compressor 106 a to operate at its maximum speed andcause the second compressor 106 b to activate.

At step 512, the compressor instructions 160 from either step 506 or 510are used to operate the compressor(s) 106 a,b. For example thecontroller 142 may provide the compressor instructions 160 to thecompressor(s) 106 a,b to cause the compressor(s) 106 a,b to operate asdetermined at step 506 or 510. At step 514, the controller 142determines a blower speed 148 at which to operate the blower 128 basedon the received indoor air temperature 144 and the indoor airtemperature setpoint 138. For example, the blower speed 148 may bedetermined based on the indoor air temperature 144 and the indoor airtemperature setpoint 138. For instance, a control loop (e.g., a PIcontrol loop) may be implemented to determine the blower speed 148 tominimize the offset 150 between the indoor air temperature 144 and IATsetpoint 138. At step 516, the controller 142 causes the blower 128 tooperate at the determined blower speed 148. For example, the controller142 may provide the blower speed 148 determined at step 514 to theblower 128, such that the blower 128 operates at the speed 148.

Modifications, additions, or omissions may be made to method 500depicted in FIG. 5. Method 500 may include more, fewer, or other steps.For example, steps may be performed in parallel or in any suitableorder. While at times discussed as controller 142, HVAC system 100, orcomponents thereof performing the steps, any suitable HVAC system orcomponents thereof may perform one or more steps of the method 500.

Example Controller

FIG. 6 is a schematic diagram of an embodiment of the controller 142.The controller 142 includes a processor 602, a memory 604, and aninput/output (I/O) interface 606.

The processor 602 includes one or more processors operably coupled tothe memory 604. The processor 602 is any electronic circuitry including,but not limited to, state machines, one or more central processing unit(CPU) chips, logic units, cores (e.g. a multi-core processor),field-programmable gate array (FPGAs), application specific integratedcircuits (ASICs), or digital signal processors (DSPs) thatcommunicatively couples to memory 604 and controls the operation of HVACsystem 100. The processor 602 may be a programmable logic device, amicrocontroller, a microprocessor, or any suitable combination of thepreceding. The processor 602 is communicatively coupled to and in signalcommunication with the memory 604. The one or more processors areconfigured to process data and may be implemented in hardware orsoftware. For example, the processor 602 may be 8-bit, 16-bit, 32-bit,64-bit or of any other suitable architecture. The processor 602 mayinclude an arithmetic logic unit (ALU) for performing arithmetic andlogic operations, processor registers that supply operands to the ALUand store the results of ALU operations, and a control unit that fetchesinstructions from memory 604 and executes them by directing thecoordinated operations of the ALU, registers, and other components. Theprocessor 602 may include other hardware and software that operates toprocess information, control the HVAC system 100, and perform any of thefunctions described herein (e.g., with respect to FIG. 6). The processor602 is not limited to a single processing device and may encompassmultiple processing devices. Similarly, the controller 142 is notlimited to a single controller but may encompass multiple controllers.

The memory 604 includes one or more disks, tape drives, or solid-statedrives, and may be used as an over-flow data storage device, to storeprograms when such programs are selected for execution, and to storeinstructions and data that are read during program execution. The memory604 may be volatile or non-volatile and may include ROM, RAM, ternarycontent-addressable memory (TCAM), dynamic random-access memory (DRAM),and static random-access memory (SRAM). The memory 604 is operable tostore measured indoor air temperatures 144 and discharge airtemperatures 154, indoor air temperature setpoints 138, adaptive DATsetpoints 156, IAT offsets 150, blower speeds 148, compressorinstructions, default DAT setpoints 202, 204, maximum temperaturedifferentials 206, thresholds 608 (e.g., any of the threshold valuesdescribed in this disclosure), the maximum speed 612 of thevariable-speed compressor 106 a, and/or any other logic and/orinstructions for performing the function described in this disclosure.As described above, the compressor instructions 160 include a compressorspeed 610 at which to operate the variable-speed compressor 106 a alongwith instructions for whether or not to operate a second compressor 106b.

The I/O interface 606 is configured to communicate data and signals withother devices. For example, the I/O interface 606 may be configured tocommunicate electrical signals with components of the HVAC system 100including the compressor 106, expansion device 114, blower 128, sensors140 a,b, motor drive 134, and thermostat 136. The I/O interface mayprovide and/or receive, for example, compressor speed signals, blowerspeed signals, temperature signals, relative humidity signals,thermostat calls, temperature setpoints, environmental conditions, andan operating mode status for the HVAC system 100 and send electricalsignals to the components of the HVAC system 100. The I/O interface 606may include ports or terminals for establishing signal communicationsbetween the controller 142 and other devices. The I/O interface 606 maybe configured to enable wired and/or wireless communications.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

To aid the Patent Office, and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants notethat they do not intend any of the appended claims to invoke 35 U.S.C. §112(f) as it exists on the date of filing hereof unless the words “meansfor” or “step for” are explicitly used in the particular claim.

What is claimed is:
 1. A heating, ventilation and air conditioning(HVAC) system, comprising: a blower configured to provide a flow of airacross an evaporator of the HVAC system; a variable-speed compressorconfigured to compress a refrigerant flowing through the HVAC system; anindoor air temperature sensor positioned and configured to measure anindoor air temperature (IAT) of the enclosed space; a discharge airtemperature sensor positioned and configured to measure a discharge airtemperature (DAT) of the flow of air downstream of the evaporator; and acontroller communicatively coupled to the blower, variable-speedcompressor, the indoor air temperature sensor, and the discharge airtemperature sensor, the controller comprising: a memory configured tostore an indoor temperature setpoint and a default discharge airtemperature setpoint; and a processor configured to: receive the IAT;receive the DAT; determine, based on a difference between the receivedIAT and the indoor temperature setpoint, that the IAT is not within athreshold range of the indoor temperature setpoint; after determiningthat the IAT is not within the threshold range of the indoor temperaturesetpoint, determine an adaptive discharge air temperature setpoint basedon the default discharge air temperature setpoint and the differencebetween the received IAT and the indoor temperature setpoint; determinea compressor speed at which to operate the variable-speed compressorbased on the adaptive discharge air temperature setpoint; and cause thevariable-speed compressor to operate at the determined compressor speed.2. The system of claim 1, wherein the processor is further configured todetermine that the IAT is not within the threshold range of the indoortemperature setpoint when the IAT is greater than the indoor temperaturesetpoint.
 3. The system of claim 1, wherein: the memory is furtherconfigured to store a default dehumidification mode discharge airtemperature setpoint and a maximum temperature differential; and theprocessor is further configured to determine the adaptive discharge airtemperature setpoint based on the default discharge air temperaturesetpoint, the difference between the received IAT and the indoortemperature setpoint, the default dehumidification mode discharge airtemperature setpoint, and the maximum temperature differential.
 4. Thesystem of claim 1, wherein the processor is further configured todetermine the compressor speed based on a difference between thereceived DAT and the adaptive discharge air temperature setpoint.
 5. Thesystem of claim 1, wherein: the HVAC system further comprises a secondcompressor; and the processor is further configured to: determine thatthe determined compressor speed is greater than a maximum speed of thevariable-speed compressor; after determining that the determinedcompressor speed is greater than the maximum speed of the variable-speedcompressor: cause the variable-speed compressor to operate at themaximum speed; and cause the second compressor to activate.
 6. Thesystem of claim 1, wherein following causing the variable-speedcompressor to operate at the determined compressor speed, the IAT iswithin a threshold value of the indoor temperature setpoint within athreshold time.
 7. The system of claim 1, wherein the processor isfurther configured to: determine a blower speed at which to operate theblower based on the received IAT and the indoor temperature setpoint;and cause the blower to operate at the determined blower speed.
 8. Amethod comprising, by a controller of a heating, ventilation and airconditioning (HVAC) system: receiving an indoor air temperature (IAT) ofan enclosed space to which conditioned air is provided by the HVACsystem; receiving a discharge air temperature (DAT) of a flow of airdownstream of an evaporator of the HVAC system; determining, based on adifference between the received IAT and the indoor temperature setpoint,that the IAT is not within a threshold range of an indoor temperaturesetpoint; after determining that the IAT is not within the thresholdrange of the indoor temperature setpoint, determining an adaptivedischarge air temperature setpoint based on a default discharge airtemperature setpoint and the difference between the received IAT and theindoor temperature setpoint; determining a compressor speed at which tooperate a variable-speed compressor of the HVAC system based on theadaptive discharge air temperature setpoint; and causing thevariable-speed compressor to operate at the determined compressor speed.9. The method of claim 8, further comprising determining that the IAT isnot within the threshold range of the indoor temperature setpoint whenthe IAT is greater than the indoor temperature setpoint.
 10. The methodof claim 8, further comprising determining that the adaptive dischargeair temperature setpoint based on the default discharge air temperaturesetpoint, the difference between the received IAT and the indoortemperature setpoint, a default dehumidification mode discharge airtemperature setpoint, and a maximum temperature differential.
 11. Themethod of claim 8, further comprising determining the compressor speedbased on a difference between the received DAT and the adaptivedischarge air temperature setpoint.
 12. The method of claim 8, furthercomprising: determining that the determined compressor speed is greaterthan a maximum speed of the variable-speed compressor; after determiningthat the determined compressor speed is greater than the maximum speedof the variable-speed compressor: causing the variable-speed compressorto operate at the maximum speed; and causing a second compressor of theHVAC system to activate.
 13. The method of claim 8, wherein followingcausing the variable-speed compressor to operate at the determinedcompressor speed, the IAT is within a threshold value of the indoortemperature setpoint within a threshold time.
 14. The method of claim 8,further comprising: determining a blower speed at which to operate ablower of the HVAC system based on the received IAT and the indoortemperature setpoint; and causing the blower to operate at thedetermined blower speed.
 15. A controller for operating a heating,ventilation, and air conditioning (HVAC) system, the controllercomprising: a memory configured to store an indoor temperature setpointand a default discharge air temperature setpoint; and a processorconfigured to: receive an indoor air temperature (IAT) of an enclosedspace to which conditioned air is provided by the HVAC system; receive adischarge air temperature (DAT) of a flow of air measured downstream ofan evaporator of the HVAC system; determine, based on a differencebetween the received IAT and the indoor temperature setpoint, that theIAT is not within a threshold range of the indoor temperature setpoint;after determining that the IAT is not within the threshold range of theindoor temperature setpoint, determine an adaptive discharge airtemperature setpoint based on the default discharge air temperaturesetpoint and the difference between the received IAT and the indoortemperature setpoint; determine a compressor speed at which to operate avariable-speed compressor of the HVAC system based on the adaptivedischarge air temperature setpoint; and cause the variable-speedcompressor to operate at the determined compressor speed.
 16. Thecontroller of claim 15, wherein the processor is further configured todetermine that the IAT is not within the threshold range of the indoortemperature setpoint when the IAT is greater than the indoor temperaturesetpoint.
 17. The controller of claim 15, wherein: the memory is furtherconfigured to store a default dehumidification mode discharge airtemperature setpoint and a maximum temperature differential; and theprocessor is further configured to determine the adaptive discharge airtemperature setpoint based on the default discharge air temperaturesetpoint, the difference between the received IAT and the indoortemperature setpoint, the default dehumidification mode discharge airtemperature setpoint, and the maximum temperature differential.
 18. Thecontroller of claim 15, wherein the processor is further configured todetermine the compressor speed based on a difference between thereceived DAT and the adaptive discharge air temperature setpoint. 19.The controller of claim 15, wherein the processor is further configuredto: determine that the determined compressor speed is greater than amaximum speed of the variable-speed compressor; after determining thatthe determined compressor speed is greater than the maximum speed of thevariable-speed compressor: cause the variable-speed compressor tooperate at the maximum speed; and cause a second compressor of the HVACsystem to activate.
 20. The controller of claim 15, wherein theprocessor is further configured to: determine a blower speed at which tooperate a blower of the HVAC system based on the received IAT and theindoor temperature setpoint; and cause the blower to operate at thedetermined blower speed.